For public keys you can put the certificates into config/certs
with .cert extension, or you could setup the public keys in your
ApplicationController by creating a OpenSSL::PKey::RSA object and
adding it to the public_keys hash:

The correct secret or public key will be used for verification based on the
current request. If the xoauth_signature_publickey parameter is
set, the corresponding public key will be used. Otherwise the consumer
secret connected to the key found in the oauth_consumer_key
parameter will be used. The singature will be verified based on this
key/secret pair and the singature method set in the parameters.

If there are OpenSocial related request parameters, you can access them
with the open_social method: